Beta-glucans have been tested for tumor therapy in mice for nearly 40 years (1,2) Several forms of mushroom derived beta-glucans are used clinically to treat cancer in Japan, including PSK (from Coriolus versicolor), Lentinan and Schizophyllan. In randomized trials in Japan, PSK has moderately, but significantly improved survival rates in some cancer trials: after gastrectomy (3,4), colorectal surgery(5,6), and esophagectomy (7) to remove primary tumors. Results have been less encouraging in breast cancer (8,9), and leukemia (10). Schizophyllan has improved survival of patients with operable gastric cancer (11), inoperable gastric cancer (12,13), and cervical cancer (14). Again, though survival differences between groups were statistically significant, these improvements were modest. While beta-glucans are not widely used by Western oncologists, beta-glucan containing botanical medicines such as Reishi and maitake (15) are widely used by U.S. cancer patients as alternative/complementary cancer therapies. These previous studies that looked for a therapeutic effect of beta-glucan did not incorporate co-administration of therapeutic monoclonal antibodies (MoAb) as part of the protocol. When beta-glucan is administered without co-administration of MoAb, its tumor cytotoxic effect requires the presence of naturally-occurring antitumor antibodies which can be quite variable among patients and even in experimental mice.
In Europe and USA beta-glucans especially from Bakers' yeast have long been employed as feed additives for animals, as dietary supplement for humans (17), in treatment of wounds (18), and as an active ingredient in skin cream formulations. The basic structural unit in beta-glucans is the β(1→3)-linked glucosyl units. Depending upon the source and method of isolation, beta-glucans have various degrees of branching and of linkages in the side chains. The frequency and hinge-structure of side chains determines its immunomodulor effect. beta-glucans of fungal and yeast origin are normally insoluble in water, but can be made soluble either by acid hydrolysis or by derivatisation introducing charged groups like -phosphate, -sulphate, -amine, -carboxymethyl and so forth to the molecule (19-20).